1. Field of the Invention
The present invention relates to a lens-interchangeable image pickup apparatus and a control method therefor.
2. Description of the Related Art
There is known a television auto-focus (TVAF) control method (hereinafter simply referred to as “TVAF control”) which is a focus control method for image pickup apparatuses. The TVAF control produces a focus signal indicating the sharpness of an image signal produced by an image sensor that photoelectrically converts an object image. A focus lens is moved such that the focus signal reaches a maximum.
For the TVAF control, the relationship between the focus signal and position of the focus lens is extremely important. In particular, it is necessary, for a lens-interchangeable camera system in which an image pickup apparatus (camera body) produces the focus signal and a lens unit detachably attached to the camera body drives the focus lens, to appropriately manage the timing of the production of the focus signal and the drive of the focus lens.
Japanese Patent Laid-Open No. 2009-258718 discloses a method of setting the timings of a drive of the focus lens for TVAF control in a lens-interchangeable camera system.
However, in a lens-interchangeable camera system in which the camera body performs the TVAF control, since respective lens units attachable to the camera body have different optical characteristics, it is difficult to perform good TVAF control for all lens units.